Tooth inclination assessment

ABSTRACT

A tooth inclination apparatus for allowing assessment of the angle of inclination of an incisor tooth or cast thereof includes a plane element providing a flat datum surface for resting against e.g. the upper molars in the maxillary plane. From the underside of the plane element projects a protractor portion with a graduated angular scale which measures the angular deviation of an indicator pin pivoted to the plane member and moved to contact the tooth whose inclination is being measured. Other mechanical or electro-optic devices may be used to determine the inclination of the incisor relative to the datum surface.

BACKGROUND OF THE INVENTION

This invention relates to the assessment of the inclination of the left,right, upper or lower incisors relative to a reference such as themaxillary plane or the mandibular plane respectively, or the occlusalplane.

The evaluation of maxillary and mandibular incisor inclinations is animportant aspect of orthodontic treatment planning, assessing treatmentprogress, as well as determining treatment outcome. Incisor inclinationhas traditionally been assessed by lateral cephalometric radiographicanalysis. However, lateral cephalometric radiograph derived axialinclinations of incisors are prone to large digitised errors. Inaddition, radiographs may cause a small but significant mitotic risk.

SUMMARY OF THE INVENTION

It is an aim of this invention to provide a valid, reliable, simple,inexpensive and non-invasive method and apparatus for recording incisorinclination.

According to one aspect, this invention provides a tooth inclinationassessment apparatus for allowing assessment of the angle of inclinationof an incisor tooth or cast thereof in or from the human or animal body,which apparatus comprises:

a datum element defining a generally flat datum surface for being placedin use against two or more upper or lower molars or pre-molars therebyto become generally aligned with the respective mandibular or maxillaryplane, and

an angular detector associated with said datum element for detecting theangular disposition relative to said datum surface of at least one ofthe upper or lower incisors respectively.

Preferably said angular detector comprises an indicator member movablymounted with respect to said datum element and arranged in use to bemoved into contact with the tooth whose angle of inclination is to bemeasured, and

an angle measurer for determining the angular orientation of saidindicator member relative to said datum element.

Preferably said indicator member is pivotally mounted with respect tosaid datum element.

In one embodiment said measurer comprises a graduated angular scalewhereby the angle of deflection of the indicator member relative to saiddatum member may be read off visually. Alternatively, said angulardetector and/or said measurer could comprise a solid state sensor whichdetects the angle of inclination of the respective incisor either bydetecting the angle of the indicator member if used, or by directdetection of the angle of the incisor. The nature, construction andoperation of such electronic or electro-optic devices will be well knownto those skilled in the art.

Preferably said indicator member extends to opposite sides of said datumsurface, to define a tooth contact portion to one side, and a measuringportion to the other, to cooperate with said angle measurer.

Preferably said datum element and said angle measurer are made up from afolded sheet element blank e.g. of paper or card plain or laminated, orof plastics material, suitably shaped.

Preferably said sheet element blank comprises two generally symmetricportions which fold together to define said first element, together witha bridging tab portion which is connected to an angular scale portion.

Preferably, said indicator member includes a shaft which is rotatablylocated in the fold region between said two symmetric portions.

The invention also extends to a kit comprising said sheet element blankin generally flat form together with an indicator element.

According to another aspect, this invention provides a method ofassessing the angle of inclination of an incisor tooth or a cast thereofin or from the human or animal body, which comprises applying to two ormore of the upper molar or lower molars or pre molars a flat datumsurface thereby to be generally aligned with the maxillary or mandibularplane respectively, said datum surface having associated therewith anangular detector for detecting the angular disposition of at least oneof the incisors, and thereby determining the angular orientation of saidincisor relative to said datum surface.

Preferably said angular detector comprises an indicator member rotatablemounted with respect to said datum surface.

Whilst the invention has been described above, it extends to anyinventive combination of the features set out above or in the followingdescription.

The invention will now be described in detail by way of example only,reference being made to the accompanying drawings in which:

FIG. 1 is a side view of an embodiment of the tooth inclinationprotractor of this invention in use on a dental cast measuring theinclination of an upper incisor to the maxillary plane;

FIG. 2 is a plan view of a blank for forming the major part of a toothinclination protractor of an embodiment of this invention;

FIG. 3 is a view of a rotatable indicator pin for use with the blank ofFIG. 2; and

FIG. 4 is a side view similar to FIG. 1, but showing an embodiment ofthe tooth inclination protractor of this invention in use in a patient'smouth.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures, the tooth inclination protractor 10 comprisesa blank 12 of suitable card or plastic sheet folded double about foldline I to provide a flat datum surface 14. From one side of the blank 12projects a tab 16 which terminates in a graduated semicircularprotractor portion 18. Rotatably secured at the origin of the protractorportion 18 is the shaft 20 of an indicator pin 22. One half of the pinprojects below the datum surface as viewed in FIG. 1 to terminate at thescale 24 of the protractor portion 18, whilst the other half of the pinprojects upwardly to be pivoted into contact with the labial surface ofthe incisor tooth whose surface of inclination is to be measured.

The blank 12 may be provided with adhesive regions 26 on the meetingsurfaces which define the datum surface 14, with an interruption toreceive the shaft 20 of the indicator pin. Likewise the meeting surfacesof the datum surface and the tab 16 may carry adhesive regions.

For flat pack, the blank may be stored in a flat form with suitablerelease sheets (not shown) on the adhesive regions, and instructions onhow to make up the tooth inclinator protractor by positioning theindicator pin 22 at the correct location at the fold line I, removingthe release sheets and then folding the blank about fold line I.Thereafter the blank is folded by 180° about fold line II to fold thetab 16 against the blank, and then by 90° about fold line III to placethe protractor portion 18 projecting normally from the datum surface,and adjacent the indicator pin 22, to produce the tooth inclinationprotractor as shown in FIG. 1.

The blank is preferably printed on one side only with the alignmentmarkings as shown in FIG. 2. The protractor may carry lines 23 on themiddle of the protractor to allow overjet to be measured.

To measure the tooth inclination in say the upper (maxillary) set ofteeth, the protractor is placed in the mouth so that the datum surface14 rests against the upper molars to define a reference surface, withthe incisor whose angle is to be measured disposed adjacent theindicator pin, and the protractor portion 18 projecting downwardly. Thepin 22 is then rotated against the lateral surface of the incisor 30 atits maximum bulbosity so that the area above and below the contact isequal so that the pin 22 is then tangential to the point of contact. Theangle of inclination is then read off the protractor scale.

The measurement may be taken on a patient directly (FIG. 4) or from acast taken from the patient's teeth (FIG. 1). In FIG. 4 the device isshown in a patient's mouth held in place by the practitioner's thumb andindex and middle fingers 32, 34, 26 respectively.

In addition, the angle of inclination of the tooth may be detected bymeans other than mechanical, e.g. electronically or by laser or anoptical device, such as a solid state sensor which detects the angulardisposition of the incisor or the indicator pin.

1. A tooth inclination assessment apparatus for allowing assessment ofthe angle of inclination of an incisor tooth or cast thereof in or fromthe human or animal body, which apparatus comprise: a datum elementdefining a generally flat datum surface (14) for being placed in useagainst two or more upper or lower molars or pre-molars thereby tobecome generally aligned with the respective mandibular or maxillaryplane, and an angular detector (18-24) associated with said datumelement for detecting the angular disposition relative to said datumsurface (14) of at least one of the upper or lower incisorsrespectively, characterised in that said angular detector (18-24)comprises an indicator member (22) pivotally mounted with respect tosaid datum surface (14) and extending to opposite sides of said datumsurface, to define a tooth contact portion to one side, and a measuringportion to the other, and an angle measurement device (18) associatedwith said datum surface (14) to allow the angle of deflection of theindicator member (22) relative to the datum surface (14) to bedetermined.
 2. A tooth inclination assessment apparatus according toclaim 1, wherein said angle measurement device (18) comprises agraduated angular scale (24) whereby the angle of deflection of theindicator member (22) relative to said datum surface (14) may be readoff visually.
 3. A tooth inclination assessment apparatus according toclaim 1, wherein said datum element and said angle measurement device(18) are made up from a folded sheet element blank (12).
 4. A toothinclination assessment apparatus according to claim 3, wherein the blank(12) is made of paper or card.
 5. A tooth inclination assessmentapparatus according to claim 4, wherein the paper or card is laminatedor coated with a waterproof or water resistant coating.
 6. A toothinclination assessment apparatus according to claim 5, wherein the blank(12) is made of plastics material.
 7. A tooth inclination assessmentapparatus according to claim 3, wherein said sheet element blank (12)comprises two generally symmetric portions which fold together to definesaid datum element, together with a bridging tab portion (16) which isconnected to an angular scale portion defining said angle measurementdevice.
 8. A tooth inclination assessment apparatus to claim 1, whereinsaid indicator member includes a according shaft (20) which is rotatablylocated in the fold region between said two symmetric portions.
 9. A kitfor making a tooth inclination assessment apparatus according to claim3, comprising said sheet element blank in generally flat form togetherwith an indicator member (22).
 10. A tooth inclination assessmentapparatus according to claim 1, wherein said datum element and saidangle measurement device (18) are integrally formed of moulded plasticsmaterial.
 11. A method of assessing the angle of inclination of anincisor tooth or a cast thereof in or from the human or animal body,which comprises applying to two or more of the upper molar or lowermolars, or pre-molars, a flat datum surface (14) thereby to be generallyaligned with the maxillary or mandibular plane respectively, said datumsurface (14) having associated therewith an angular detector (18-24) fordetecting the angular disposition of at least one of the incisors, andthereby determining the angular orientation of said incisor relative tosaid datum surface 14, wherein said angular detector (18-24) comprisesan indicator member (22) pivotally mounted with respect to said datumsurface (14) and extending to opposite sides of said datum surface, todefine a tooth contact portion to one side, and a measuring portion tothe other, and an angle measurement device (18) associated with saiddatum surface (14) to allow the angle of deflection of the indicatormember (22) relative to the datum surface (14) to be determined.